Method for loosening stuck drill pipe



Oct. 8, 1957 w. c. ERWIN METHOD FOR LOOSEN'IENG STUCK DRILL PIPE FiledSept. 22, 1955 INVENTOR. WELDON c. ERWIN TTORNEYS METHOD FOR LOOSENIN GSTUCK DRILL PIPE Weldon C. Erwin, South Gate, Calif. ApplicationSeptember 22, 1955, Serial No. 535,840

7 Claims. (Cl. 166-43) This invention generally relates to a method ofloosening and freeing a drill pipe or equivalent string of pipe, casing,or tubing which has become stuck in the course of well operations. Theinvention will be illustratively described in connection with oildrilling operations where solid materials have settled or foreignobjects or particles have lodged in the annulus between the operatingstring and the side walls of the well bore, although it will beappreciated that the method may be advantageously employed in otheranalogous applications. In its use in oil well operations, the method ofthe present invention, in common with certain methods here tofore usedfor the same purpose, is based upon creating a fluid surge within thewell by varying the hydrostatic head of the liquid or circulating mud inthe well. In the hydraulic methods previously used, it is usuallyessential that a normally closed chamber be lowered down within the wellto a given location, and thereafter suddenly opened to admit thecirculating fluid, whereby a fluid surge is effected tending to jarloose the stuck section of the drill pipe string. In other methodspresently employed, it is required that the pipe be severed or partedabove the stuck point by unscrewing, cutting, or blasting, and the freeportion thereafter removed from the Well bore, before the actual stuckportion, or fish, as it is commonly called, can be recovered.

The primary object, therefore, of the present invention is to provide amethod of loosening and freeing a stuck drill pipe or equivalent tubularstring without the necessity of lowering or forming a closed chamberwithin the drill pipe, and without the necessity of severing the drillpipe string as a preliminary step before the utilization of 4onventional recovery methods and devices.

A more specific object of the present invention is to provide animproved method of loosening and freeing a stuck drill pipe orequivalent tubular string wherein no additional apparatus or tools needbe inserted into the well, and in which the hydrostatic column withinthe well is instead used as the primary means of creating the hydraulicor fluid surge required.

Briefly, these and other objects of the present invention are achievedby providing a controlled pressure source on the surface as a means ofcreating a pressure differential between the fluid column in theannulus, defined hv the drill string and the side walls of the wellbore, and the fluid column within the drill pipe. In order to establishthis condition, the upper end of the drill pipe is closed off andconnected to the pressure source. Thereafter, the pressure source isused as a means of transmitting compressed air or gas, or conceivably afluid United tates Patent 9 may be passed from the well at ground levelthrough a conduit to a tank or reservoir for temporary storage or to themud pit.

After the hydrostatic column within the drill pipe has been lowered to apredetermined location according to the pressure differential required,the pressure source may then be actuated so as to release the compressedgas from within the drill pipe string. In response to the releasing ofthe gaseous pressure, a surging inward fluid flow will occur from theannulus back through the bit opening and'up into the drill pipe. Thesurging flow will tend to wash loose any material which may haveaccumulated or settled in the annulus as well as dislodge any foreignobjects stuck between the drill pipe and the well side walls.

If the initial injection and release of the compressed gas Within thedrill pipe does not suflice to loosen-the stuck section of pipe, thecontrol pressure source may be intermittently actuated to close off andrelease compressed gas within the drill pipe, as by opening and closinga control valve. As a result, a fluid ram effect will be createdimparting a vibrating and jarring action to the drill pipe string.

According to the particular well conditions, an additional step as apart of this method may be required in order to prevent well caving orsloughing. This additional step consists of reinjecting or pumping fluidback into the annulus at substantially the same rate it flows back intothe drill pipe in response to a releasing of the pressurized gases fromwithin the pipe. In this manner, a full hydrostatic column can bemaintained in the annulus so that the circulating fluid level will notdrop below the bottom of the surface casing to create the possibility ofsloughing or the danger of a well blowout in the event high pressuresexist in the surrounding formations.

A better understanding of the present invention will be had by referenceto the accompanying drawings, which merely illustrate one conceivableapparatus for the performance of the method, and in which:

Figure 1 is an elevational view of a typical oil Well and drilling rig,in which the drill pipe is stuck because of materials and foreignobjects lodged between the drill pipe and well side walls; and,

Figure 2 is a view of the oil well of Figure 1 after pressurized gas hasbeen injected into the drill pipe from the surface.

There is shown in Figure l a derrick 10 disposed above an oil well 11.The well is provided with a casing 12, and positioned Within the casingis an operating string or drill pipe 13. The drill pipe 13 terminates atits lower end in a conventional bit 14 having an opening 15.

In the annulus 9 formed by the drill pipe 13 and the well side walls orcasing 12, there is shown a layer of impacted material 16 and foreignobjects 17, near the bottom portion of the drill pipe 13, which havesettled so as to prevent or hamper further movement of the drill pipe13.

The entire well 11, as in conventional oil drilling operations, isfilled with a circulating fluid or mud 18, which flows down through thedrill pipe 13, out through the bit opening 15 and then up through theannulus 9 between the drill pipe and the casing 12 to flow out at thesurface of the well into a mud ditch (not shown) and thereafter into amud pond or pit 19. The mud 18 is recirculated through the well from thepit 19 by a conventional slush pump 20 and valving 21 to thereafter passthrough a rotary hose 22 back into the drill pipe 13 through aconventional rotary table 23. I

The method of the present invention is primarily directed towardproviding a controlled source of pressurized fluid, preferably gas orair. In consequence, there is additionally provided at the surface ofthe well awe iliary equipment in the form of a pressure system,generally designated by the numeral 24. This pressure system 24 isschematically shown as comprising a plurality of combustion chambers 25,each of which has aninlet 26 connecting into a manifold 27. The manifold27 would, in turn, include appropriate high pressure control valvingindicated at 28 and preferably located within the drill stem or pipe 13and pressure relief valving indicated at 29. A flexible hose 30, similarto the rotary hose 22 used in connection with the circulating system,could be provided for connection between the manifold 27 and the drillpipe 13.

In, the practice of the method of the present invention, a rapid burningfuel (similar'tothat used inrockets and the like) is placed into thecombustion chambers 25 where it is ignited or detonated, to in turncreate high pressure gases that will pass through the valves 26 andthereafter into the manifold 27 to pass down into the drill pipe 13 asshown in Figure 2 at 31. A conventional fuel comprised of sticks ofcordite, for example, encased in an inert material within the combustionchambers 25 might be employed for this purpose. By encasing the corditesticks in an inert material, a controlled burning rate may be achievedover a period of sixty seconds or longer with a consequent gradual buildup of pressure within the drill pipe 13. A plurality of electricalheating elements or coils couldbe located within the combustion chambersadjacent the end faces of the sticks, and might be connected to asuitable source of power at the well location for initiating the burningof the fuel within the combustion chambers. The inlet valves 26 areprovided with check valve devices so that the high pressure gases formedin the individual combustion chambers 25 will have a cumulative effect,and whereby each chamber 25 actually operates as an individual unit. Itis feasible, therefore, to utilize any number or combination of thecombustion chambers 25 as a means of creating a particular pressure andvolume of gas required.

Assuming that the drill pipe in the well 11 has become stuck because ofthe impacted material 16 and the foreign objects 17, the circulatingsystem is first shut off, and the necessary steps are taken to properlyclose and seal off the drill pipe 13 at the surface of the well, as bythe control valve 28, according to the particular type of equipmentbeing used. Thereafter, the flexible hose 30 is connected to the closedofl end of the drill pipe 13 so as to communicate thereto through thevalve 28. The pressure system 24 is then actuated so as to pass thepressurized gases 31 from the individual combustion chambers 25 throughthe respective inlet valves 26, and thereafter into the manifold 27,through the control valving 28, and the flexible hose 3% down into thedrill pipe 13. As a consequence, the mud 18, normally having ahydrostatic head rising within the well and within the drill pipe 13 tothe surface, is forced down to a predetermined level, L, as shown inFigure 2, by the pressurized gases 31. The mud 18, being urgeddownwardly, will pass through the bit opening 15 and thereafter into theannulus 9 between the drill pipe 13 and the casing 16, which will resultin an overflow of mud from the annulus into the mud ditch, to thereafterpass to the mud pit 19.

When the column of circulating mud has stabilized at the level L,according to the pressure of the gases 31, it will be evident that apressure differential will exist between the column of mud within thedrill pipe 13 and the column of mud in the annulus 3, proportional tothe distance from the level L to the surface. This level may be readilyascertained by measuring the volume of fluid displaced from the annulus,at the surface of the well. At this time, the control valving 28 andrelief valving 29 may be actuated so as to open a passage from the drillpipe 13 through the hose 36 and manifold 27 to atmosphere. Inconsequence, the gases 31 will suddenly, in response to the opening ofthis passage, expand upwardly out of the drill pipe. In response to theescape of the gases 31, the unbalanced columns of the circulating mud 18will tend to re-level, and a violent surging flow will occur as the mudwithin the annulus 9 passes back through the bit opening 15 and up intothe drill pipe 13. This surging fluid movement will frequently besufficient to wash away the impacted material 16 and dislodge theforeign objects 17. i

In the event that the initial injection and release of the gases'31 isnot suflicient to accomplish the loosening of the drill pipe 13, thecontrol valving 28may be intermittently opened and closed, before thegases 31 have been totally expelled, to create a ramming fluid actionvibrating and jarring the drill pipe 13 while at the same time washingthrough the impacted material 16 and foreign objects 17. Theintermittent changing of the level of the fluid head within the drillpipe 13 will generally free the pipe and loosen it from the material 16and objects 17.

It is desirable, in accordance with conventional practice, that thedrilling cable, as at 32 in Figure 1, be placed in tension so as toexert an upward strain on the drill pipe 19 while the gases 31 are beinginjected and expelled; also, torque may be applied to the drill pipe inorder to supplement the surging action of the circulating fluid or mudin freeing the stuck portion.

It will be appreciated, that in order to prevent cave-ins or damage tothe casing 12, as aresult of high pressure formations existing in thearea surrounding the well 11, it is desirable to maintain a high levelof circulating mud 18 in the annulus 9 at all times. Therefore, as thehydrostatic column within the annulus is decreased as it flows back intothe drill pipe 13, it is important that the annulus be replenished withmud at substantially the same rate that it being displaced. For thisreason, under most well conditions, at the time the gases 31 are beingexpelled to the atmosphere, the circulating system should be re-actuatedby starting the pump 20 and operating the valving 21 so as to bypass thehose 22 and cause a flow of circulating mud to pass back into theannulus of the well, as through a conventional fill line 33. Not onlywill the replenishing of the circulating mud 18 into the annulus serveto prevent possible cave-ins, but it will also have a tendency tolengthen the time during which the pressure differential between thecolumn within the drill pipe 13 and in the annulus is maintained.

It will be evident, that although a preferredpressure system 24 has beenshown for the performance of the method of this invention, that othersystems are equally feasible. For example, air compressors or highpressure gas lines, or anyother apparatus capable of delivering fluidunder the requisite pressure conditions may be utilized. The combustionchambers 25 are advantageous because of their portability and the factthat they do not require connecting power or pressure and are thus moreversatile and adaptable for use at most drilling locations.

It is further conceivable under certain conditions that the compressedgases might be forced into the annulus to create a reversed flow. It isapparent, therefore, that certain changes may be made in the method,according to the application involved, without departing from the spiritand scope of the invention.

What is claimed is:

1. In well operations in which a hydrostatic column of circulating mudis normally disposed in the well and within a tubular string positionedwithin the well and spaced apart from the side walls, a method forloosening a stuck portion of said string comprising the steps of:closing off the upper end of said string to the circulation of mud;connecting a controlled pressure source of fluid to said upper end forcommunication therethrough into said string; actuating said source so asto inject under pressure into said string a given volume of said fluidto thereby decrease the hydrostatic column within said string; andactuating said source to release said pressure,

whereby a reverse surging flow will occur increasing the hydrostaticcolumn within said string.

2. In well drilling operations in which a hydrostatic column ofcirculating mud is normally disposed in the well and within theoperating string of pipe, a method for loosening a stuck portion of saidstring comprising the steps of: closing off the upper end of said stringto the circulation of mud; connecting a controlled pressure source offluid to said upper end for communication therethrough into saidoperating string; actuating said source so as to inject under pressureinto said string a given volume of said fluid to thereby decrease thehydro static column within said string; and actuating said source torelease said pressure, whereby a reverse surging flow will occurincreasing the hydrostatic column within said string.

3. The method according to claim 1, in which said fluid comprises acompressed gas.

4. The method according to claim 1, in which said fluid comprises aliquid having a lower specific gravity than said circulating mud.

5. In well drilling operations in which a hydrostatic column ofcirculating mud is normally disposed in the well and within theoperating string of pipe, a method for loosening a stuck portion of saidstring comprising the steps of: closing off the upper end of said stringto the circulation of mud; connecting a controlled pressure source ofgas to said upper end for communication therethrough into said operatingstring; actuating said source so as to inject under pressure into saidstring a given volume of said gas to thereby decrease the hydrostaticcolumn of mud within said string by effecting an outward flow through alower opening into the annulus between said string and the well sidewalls; actuating said source to release said pressure, whereby an inwardsurging flow will occur from the column within said annulus back throughsaid lower opening into said operating string; and reinjectingcirculating mud into said annulus at substantially the same rate it isdisplaced therefrom during its flow back into said operating string.

6. In well drilling operations in which a hydrostatic column ofcirculating mud is normally disposed in the well and within theoperating string of pipe, a method for loosening a stuck portion of saidstring comprising the steps of: closing ofl? the upper end of saidstring to the circulation of mud; connecting a controlled pressuresource of gas to said upper end for communication therethrough into saidoperating string; actuating said source so as to inject under pressureinto said string a given volume of said gas to thereby decrease thehydrostatic column of mud within said string by effecting an outwardflow through a lower opening into the annulus between said string andthe well side walls; and actuating said source to intermittently releasesaid pressure to cause a corresponding intermittent changing of level offluid within the drill pipe and create a ramming fluid action withinsaid operating string.

7. The method according to claim 6, in which a torque and axial strainis applied to said operating string.

References Cited in the file of this patent UNITED STATES PATENTS1,774,640 Dunn Sept. 2, 1930 2,139,076 Gates Dec. 6, 1938 2,163,115Beckman June 20, 1939 2,361,558 Mason Oct. 31, 1944

